The STATEMAP program is a component of the National Geologic Mapping Act of 1992 (renewed for ten years in 2009). STATEMAP is a matching fund program whereby State general funds are matched one-to-one with federal funds to support geologic mapping by the states. The Arizona Geological Survey (AZGS) has participated in the STATEMAP program since its inception, and has produced 1:24,000-scale geologic maps of a large fraction of Arizona with funding from this program (Fig. 1). Three new geologic maps (five 7.5’ Quadrangles), currently being drafted but otherwise complete, represent the products of the 2012-2013 field season (STATEMAP 2013; See list below). Five more geologic maps are currently in progress for STATEMAP 2014 (Fig. 1). For the September 2014 to September 2015 STATEMAP contract period, Arizona will receive $171,339 from the US Geological Survey (USGS), which administers the STATEMAP program, for new geologic mapping, to be matched by an equal or slightly greater amount of State funds. Over the past 20 years, the AZGS has received $3,772,395 in federal funds from the STATEMAP program.
Geologic map areas are determined following recommendations from the Arizona Geologic Mapping Advisory Committee (GMAC), which consists of about a dozen representatives of environmental consulting companies and individual consultants, mining and mineral-exploration interests, government agencies, and one university faculty member. The GMAC meets once a year to make recommendations. Based on GMAC recommendations in 2013, the five 7.5’ Quadrangles will be mapped with these funds during the 2014-2015 mapping season, are as follows:
(1) The Corona de Tucson 7.5’ Quadrangle is located south of Tucson at the foot of the northern Santa Rita Mountains (Fig. 2). This quadrangle was selected for mapping primarily because it is located near several large porphyry copper deposits and it encompasses the Quaternary Santa Rita fault zone. In addition, there are issues and controversies associated with past geologic mapping. Previous USGS mapping in the Santa Rita Mountains (Drewes, 1971, 1972) identified faults that were mapped as depositional contacts by AZGS geologists during previous STATEMAP mapping (Fig. 3; Ferguson et al., 2009).
(2) Two Quadrangles planned for mapping are located along the Colorado River in Mohave and La Paz Counties (Fig. 4). This area was selected for mapping largely because of interest in aggregate deposits associated with the Colorado River, and because population growth rates and environmental geology concerns are high in the Colorado River Valley. In addition, very little is known about the geology of an old mining district that is within one of the Quadrangles except that it is near the historic Cinnabar mercury mine.
(3) Two Quadrangles planned for mapping are located in the Oatman area in Mohave County, and include the Oatman 7.5’ Quadrangle (Fig. 5). This area was selected partly because the Oatman mining district is located on epithermal vein deposits that have yielded ~2 million ounces of gold, which is more than any other gold deposit in Arizona (some large porphyry copper deposits have yielded similar or larger amounts of gold). The geology of the district is incompletely understood, although a recent study (Ferguson et al., 2013) determined that a large caldera forms the western part of the district and that this caldera was the source of the widely distributed Peach Spring Tuff (Young and Brennan, 1976; Glazner et al., 1986). The historic and currently active Moss gold mine in the Oatman district is actually inside the caldera.
Cook, J.P., 2013, Geologic map of the Artesia 7 ½' Quadrangle and the northeastern corner of the Mt. Graham 7 ½' Quadrangle, Graham County, Arizona: Arizona Geological Survey Digital Geologic Map DGM-106, scale 1:24,000.
Cook, J.P., and Youberg, A., 2013, Geologic map of the Safford 7 ½' Quadrangle, Graham County, Arizona: Arizona Geological Survey Digital Geologic Map DGM-104, scale 1:24,000.
Ferguson, C.A., and Pearthree, P.A., 2013, Geologic map of the Sullivan Buttes 7 ½' Quadrangle, Yavapai County, Arizona: Arizona Geological Survey Digital Geologic Map DGM-102, scale 1:24,000.
Johnson, B.J., Cook, J.P., Pearthree, P.A., and Ferguson, C.A., 2013, Geologic map of the Prescott Valley South 7 ½' Quadrangle, Yavapai County, Arizona: Arizona Geological Survey Digital Geologic Map DGM-103, scale 1:24,000.
Spencer, J.E., Richard, S.M., Johnson, B.J., Love, D.S., Pearthree, P.A., and Reynolds, S.J., 2013, Geologic map of the Artillery Peak and Rawhide Wash 7 ½' Quadrangles, Mohave and La Paz Counties, Arizona: Arizona Geological Survey Digital Geologic Map DGM-100, 2 sheets, scale 1:24,000.
Youberg, A., 2013, Geologic map of the Thatcher 7 ½' Quadrangle, Graham County, Arizona: Arizona Geological Survey Digital Geologic Map DGM-105, scale 1:24,000.
Drewes, H.D., 1971, Geologic map of the Sahuarita quadrangle, southeast of Tucson, Pima County, Arizona: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-613, 1 sheet, scale 1:48,000.
Drewes, H., 1972, Structural geology of the Santa Rita Mountains, southeast of Tucson, Arizona: U.S. Geological Survey Professional Paper 748, 35 p., with map sheets, scales 1:100,000 (1 sheet) and 1:12,000 (3 sheets).
Ferguson, C.A., Johnson, B.J., Pearthree, P.A., Spencer, J.E., Shipman, T.C., and Cook, J.P., 2009, Geologic map of the Helvetia 7 ½' Quadrangle, Pima County, Arizona: Arizona Geological Survey Open-File Report 09-06, version 1.0, scale 1:24,000.
Ferguson, C.A., McIntosh, W.C., and Miller, C.F., 2013, Silver Creek caldera – The tectonically dismembered source of the Peach Spring Tuff: Geology, p. 3-6; doi: 10.1130/G33551.1.
Glazner, A.F., Nielson, J.E., Howard, K.A., and Miller, D.A., 1986, Correlation of the Peach Springs Tuff, a large-volume Miocene ignimbrite sheet in California and Arizona: Geology, v. 14, n. 10, p. 840-843.
Young, R.A., and Brennan, W. J., 1974, The Peach Springs Tuff -- Its bearing on structural evolution of the Colorado Plateau and development of Cenozoic drainage in Mohave County, Arizona: Geological Society of America Bulletin, v. 85, p. 83-90.